Various grain crops, for example corn, are stored in a silo until needed for feeding livestock. The usual method for removing a portion of the silage from a silo is to employ a silo unloading apparatus which operates to dislodge the upper layer of silage and move it to the outer wall of the silo where it is discharged through an open door in the side of the silo and then transferred to a conveyor or other means for supplying the animals to be fed.
Some silo unloaders include means for forming a cylindrical channel along the center of the mass of silage as the silo is being filled. See for example U.S. Pat. Nos. 3,794,190, 3,075,657, 3,908,840 and 3,368,703. The central channel was intended to provide a discharge channel for removal of silage through the bottom of the silo. However, this system has not proved to be effective and finds little use today.
Other proposals include various means for forming a vertical channel within the silage extending along the inside surface of the wall of the silo. One of these devices is a cylindrical torpedo that is winched up along the wall while the silo is being filled. Torpedoes are used only slightly because it is difficult to accurately determine the position of a torpedo relative to silage being loaded into a silo and it tends to move sideways as it is winched upwards. Another proposal, see U.S. Pat. No. 3,063,585, involves using an electric drill having radial blades mounted for rotation about a vertical shaft through silage upward along a track secured to the inside of the wall of a silo after it had been filled. This device, however, does not present a useful solution because of the difficulty of tunneling through silage that has become firmly packed into a relatively hardened mass of material.
A principal object of the present invention is to provide a silage-tunneling apparatus that is capable of forming a vertical tunnel in silage packed within a silo. Another is to provide a silage-tunneling apparatus that does not require the addition of a vertical track to the interior surface of the wall of the silo. A further main object is to provide a silage-tunneling apparatus which can be operated at sufficiently low speed when driven with an electric motor to develop the power necessary to form a vertical tunnel in silage firmly packed within a silo. Other objects will become apparent from the following detailed description of this invention.